A veteran Manhattan lawyer is suing Assembly Speaker Sheldon Silver based on novel claims concerning the once-confidential settlement Silver entered into with two alleged victims of former Assemblyman Vito Lopez.

Howard Gotbetter alleges Silver is guilty of breach of contract — his oath of office; acting in ways that did not benefit the taxpayers of New York; and gross negligence by failing to protect victims of sexual harassment.

The suit involves Silver's agreement to use of $103,080 in public funds to settle sexual harassment claims brought by two women who worked for Lopez when the Brooklyn Democrat served in the Assembly. After the 2012 settlement, Lopez allegedly continued to harass more women; the terms of the deal ended up becoming public a year ago. Silver apologized for mishandling the matter by failing to refer it to a legislative ethics panel.

Gotbetter said on Monday that he also intends to sue Silver for $24,000, the amount the lawyer believes the Democratic leader owes taxpayers for his years of commuting to Albany and keeping frequent-flier miles.

"My client is the taxpayers of New York," said Gotbetter, a 1955 graduate of New York University Law School.

Gotbetter, who has been practicing for 55 years, said he is using causes of action in his Lopez-related suit that have never been tried before. He argues that lawmakers have no property or ownership rights to their state office, and hold their posts under a legal agreement with New Yorkers. When they take an oath to "faithfully discharge the duties of the position," they are entering a contract, he argues.

"The Vito Lopez debacle and scandal involved sexual harassment claims resulting in over $100,000 in payments of taxpayer moneys hidden by Silver in total and utter breach and violation of Silver's obligations," Gotbetter wrote in his Sept. 27 complaint.

His goal, Gotbetter said, is to compel Silver to pay back the settlement money to state taxpayers, with interest, plus fees and costs for the lawsuit as well as fees the public is paying for Silver's private lawyers.

The suit is one of several targeting Silver's settlement with Lopez, who resigned his position this year under fire.